Method of forming tappets



Feb. 16, 1932. c. B. MCDONALD 1,845,311

METHOD OF FORMING TAPPETS Filed July 2, 1928 jumu.

amuenfoz Patented Feb. 16, 1932 UNETED STATES "PATENT OFFICE CHARLES B.MCDONALD, 013 DETROIT, MICHIGAN, ASSIGNOR TO WILGOX PRODUCTS COR-PORATION, F DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN METHOD OFFORMING TAPPETS Application filed July 2., 1928. Serial No. 289,887.

to obtain hardened surfaces for engaging the cam and also the bearing inwhich the tappet reciprocates. It has also been found that chilled castiron is a desirable material for forming such surfaces. However, it isalso necessary to form a threaded socket for receivin the adjustingscrews. Chilled cast iron is too hard to permit of machining andtherefore it is usual to construct the tappet or the portion thereof inwhich the threaded socket is formed, of metal sufficiently soft formachining.

It is the object of the invention to obtain a construction in which allof the wearing surfaces are formed of chilled cast iron but which at thesame time is provided with a soft core that may be bored and threadedfor receiving the adjusting screw. To this end the invention consists inthe process and product as hereinafter set forth.

As shown in Figure 1 A is a blank having a portion B which correspondsto the for of the tappet together with a sprue portion C and a portion Dintermediate portions B and C which is of smaller diameter. This blankis cast in a chill, the metal being fed into the portion B from thesprue portion so as to compensate for shrinkage and to obtain therequired density in the full length of the portion B. The chill willimpart to the surface portions of the metal adjacent thereto a greatdegree of hardness but the hardening elfect does not extend into thecentral core. If, however, the blank were only of a length equal to thefinished tappet its end portions as well as its sides would be hardenedand it would be impossible to drill or machine the core. This diliicultyI have avoided by providing the extended sprue portion together with thecontracted portion D which permits of breaking off the sprue therebyexposing the soft core. Thus to finish the tappet it is only necessaryto drill and thread as indicated at E. I

The construction shown in Figure 2 is the same as that shown in Figure 1with the exception that an enlarged head F is formed to constitute thecam follower. This head is integral with the cylindrical portion forengaging the bearing, and a groove G is preferably formed between theseportions to facilitate the grinding of the cylinder.

What I claim as my invention is:

1. The method of forming tappets which consists in casting a chilledblank of a length greater than the finished tappet, severing a portionof said length to expose the end of the soft core and in then machininga socket in said core.

2. The method of forming tappets which consists in casting a chilledblank of greater length than the finished tappet provided with a sprueportion for supplying the metal compensating for shrinkage, in severingsaid sprue portion to expose the end of a soft core in the remainingportion and in machining said core to form a socket therein.

3. The method of forming tappets which consists incasting a chilledblank of a length greater than that of the finished tappet, the

extra length forming a sprue portion and a contracted portionintermediate said sprue portion and the tappet proper, in severing theblank in the plane of said contracted portion to expose the end of asoft core and in machining to form a socket in said core.

4. The method of forming tappets which consists in casting a chilledblank with a soft core, exposing the soft core atone end of the blank,and in then machining a. socket in said core.

5. The method of forming a tappet which consists in casting a chilledblank with a soft core, cutting the said blank to expose the soft coreat one end of the blank, and'in then forming a socket in said corethrough the exposed portion thereof.

In testimony whereof I aflix my signature.

CHARLES B. MCDONALD.

